Wednesday, October 14, 2015

Musings from Priyadarshini Karve: Sampada ELFD Gen II!

We had launched Sampada ELFD stove for institutional cooking last year, and it has generated a lot of excitement wherever we have demonstrated it. You can also see a video of its operation on our YouTube channel. We are now bringing a second generation of the Sampada ELFD stove, which is much simpler to operate, is more versatile for different types of cooking operation, and cost wise is on par with the simplest electricity powered forced draft stoves available in the market. What is more, we now also have a stove model for households!

Sampada ELFD is a forced draft stove - it uses artificially controlled air flow to introduce excess air in the fuel chamber, to help burn up the hot combustible gases and particulates, with minimal emissions. This is the only way a solid biomass burning stove can meet the air quality standards prescribed by the World Health Organisation. In most forced draft stoves, the draft is produced with the help of a fan or a blower run by electric power. In the simplest designs the fan/blower is powered simply by plugging into the wall socket, just as we run a table fan, on grid electricity. More sophisticated designs incorporate a fan or blower run on a battery, which can be charged by either grid electricity or by solar PV etc.

There is currently one very sophisticated stove in the market, which uses the heat of the stove to charge a battery, which can run the fan and also charge a cell phone.

All of these designs were developed based on the assumption that we need forced draft, and the only way to achieve it is to use a fan/blower. The focus was on the 'means' rather than the 'end result'. We focused on the end result, and explored other avenues of creating forced draft. In nature, wind is created by pressure difference in the air. So we used a process that comes closer to nature, and does not require either grid power or electricity. In our system, the heat of the stove is used for generating pressurised steam, which is released in a jet at the entrance to the fuel chamber where normally a fan or blower would be attached. The steam jet creates a pressure differential, and pulls in air along with it, giving us the desired effect.

Our collaborators, Electrofabrik, must of course get the main credit for the development of the ELFD mechanism. The engineering inputs that have gone into this ingenious design have come entirely from them.

I have written in the musings before about how we need to shift the focus to the 'service' provided, rather than the obvious source for providing the service. There are always various ways to achieve the same end result, and exploring these can lead to interesting options. The way Sampada ELFD design has come about is a good example of this.